The present technology relates to a non-contact communication device, and more particularly, to a non-contact communication device capable of improving communication performance of non-contact communication.
An integrated circuit (IC) card for exchanging data through non-contact communication is much more convenient to use than a medium (for example, a magnetic card) in which data reading/writing is performed in a contact state. In recent years, for example, since the IC card has been widely utilized in ticket systems of railroad systems and the like, electronic money systems for payment in stores such as convenience stores, entrance and exit systems for managing entrances and exits to/from rooms of a company, etc. demands therefor have increased more and more.
For example, an IC card of an entrance and exit system has an IC chip with an entrance and exit ID (identification) as information for identifying a user possessing the IC card, and a photograph of a user's face and/or a name is displayed on the surface thereof.
In the entrance and exit system, a reader/writer (R/W) is installed around a doorway of a room to perform non-contact communication with the IC card, and if a user passes the IC card over the R/W, data exchange and other processes are quickly performed between the IC card and the R/W through non-contact communication in order to permit the entrance and exit to/from the room.
Non-contact communication devices for performing non-contact communication with the R/W include a portable terminal such as a cellular phone having a function of the IC card, a token-shaped IC tag (a wireless tag) in which the top and bottom of an IC chip are sandwiched by a resin case, and the like in addition to a card-shaped IC card, and the portable terminal or the IC tag has also been spread as a non-contact communication device, in addition to the IC card.
Here, a communication device performing non-contact communication will also be referred to as a non-contact communication device.
Both the R/W and the IC card, which transmit data to each other through non-contact communication, are non-contact communication devices.
The R/W outputs a radio frequency (RF) signal by itself, modulates the RF signal, and transmits data.
Meanwhile, for example, the IC card and the like having no power supply is driven by obtaining power from the RF signal output from the R/W, and load-modulates the RF signal to transmit data.
Hereinafter, a non-contact communication device such as the R/W, which outputs an RF signal and modulates the RF signal to transmit data, will also be appropriately referred to as an initiator, and a non-contact communication device such as the IC card, which is driven by obtaining power from the RF signal output from the initiator and load-modulates the RF signal to transmit data, will also be referred to as a target.
The IC card and the like serving as the target include electronic parts such as an IC chip, one (loop) coil, or a capacitor.
That is, in the IC card, for example, the IC chip, the capacitor and the like are connected to the coil as an antenna. If the IC card approaches the R/W and the like serving as the initiator, current flows through the coil serving as the antenna of the IC card due to electromagnetic induction by the RF signal output from the R/W, and the IC chip connected to the coil is driven by power obtained from the current.
In addition, by the capacitor connected to the coil serving as the antenna, a resonance frequency of a resonance circuit including the capacitor and the coil is adjusted.
For example, Japanese Unexamined Patent Application Publication No. 2007-328634 has proposed an R/W capable of simply adjusting a resonance frequency by closely electromagnetically coupling a main antenna coil and a sub-antenna coil to each other such that a coupling coefficient approaches 1 to a maximum extent, wherein the main antenna coil and the sub-antenna coil are not directly electrically connected to each other.
Furthermore, for example, Japanese Unexamined Patent Application Publication No. 2004-145453 has proposed an IC module which allows a single semiconductor circuit chip to integrally have an R/W function and an IC card function through a first loop antenna connected to an input/output terminal of a card IC function unit, and a second loop antenna connected to an input/output terminal of a reader/writer function unit and arranged inside the first loop antenna.